I've said more times than I can count that the key to understanding most theological apologetics questions on the topics of exclusivism, hell (its existence and duration), the need for (and meaning of) the cross, the judgment of the Canaanites, God's justice, grace, and why we praise Him is a grasp of God's holiness and, by contrast, our sinfulness.
And the book I recommend more often than any other to help with this understanding is R.C. Sproul's The Holiness of God. Which is why I wanted to let you know that right now this book is free for Kindle on Amazon. But it's only for a limited time, and I've no idea how limited. Sometimes these deals only last a day, so get it while you can.